With increasing traffic entering a network, a network device becomes larger and higher in performance, thereby causing larger power consumption and higher cost.
On the other hand, in the current network, excess circuits and devices are arranged to accommodate traffic in many cases, and it is expected that the optimum arrangement of circuits and devices may realize power saving and lower cost of the entire network (hereafter referred to as cost including power and amount of money). However, since the appropriate arrangement of circuits and devices depends on the traffic transfer state (path route), it is important to totally consider the arrangement of the traffic path, circuits, devices, etc. to derive a cost-saving network configuration.
On the other hand, with the network design by conventional labor, there is the problem that it is hard to design a network for process a large number of parameters by considering the dependence among various design elements (path, circuit, device, etc.). Therefore, the technology of automatically designing a network configuration for minimum power (lowest cost, or the minimum cost totally) is requested by generating a systematic design process with each design element taken into account.
There is the conventional technology described in the non-patent document 1 as a system published lately to perform automated and integral designing for a traffic transfer path and a network device configuration.
This document discloses a method of designing a network by solving a mathematical programming problem by performing traffic flow design to each path candidate and chassis configuration design so that the amount of power consumption may be minimized for the device configuration accommodating a traffic demand.
However, the prior art has the following problem.    1. The network design may not be performed with various path configuration patterns and port use modes taken into account.
Since the smallest link cost path regulated by routing protocol is assumed for each site connection, the path search range is limited, the port type having various transfer rates may not be selected, or detailed port use modes such as link aggregation etc.    2. A design arithmetic operation is not performed in a large network.
There is a large design problem, and a design arithmetic operation may not be realized depending on the performance of the machine for performing arithmetic operations and the performance of the software (solver) for solving the mathematical programming problem.
Therefore, the prior art has no function of performing the integral designing of a device by considering various path states and port use modes, and it is very hard to perform designing arithmetic operations in a practical time period in solving the design problem with a large real network environment. The practical time period refers to the time period appropriate for performing a practical operation as the time required for network design. For example, a practical time period refers to one day or several hours. When a longer time is taken by the operation using a network design device than by manual labor in performing a practical network designing operation, it is not a practical time period.
The prior art may provide a demand as a probability variable, generates a probable constraint, and performs network design as a mathematical programming problem.